Self-extinguishing ethylene copolymer foams comprising a ternary mixture of an antimony compound, a halogen-containing compound and a bromine compound

ABSTRACT

Compositions of the class of flame-retardant or selfextinguishing ethylene and vinyl alkanoate copolymer foams, useful as insulation, are described. Said foams are relatively lightly loaded with either a binary flame retardant mixture of (1) an antimony compound and (2) a halogen-containing aliphatic or cycloaliphatic compound of particular specificity or a ternary flame-retardant mixture including (1) and (2), and, (3) a bromine-containing aromatic or acyclic compound of particular specificity.

United States Patent Raley, Jr. 1 June 6, 1972 [54] SELF-EXTINGUISHINGETHYLENE [56] References Cited COPOLYMER FOAMS COMPRISING A UNITEDSTATES PATENTS TERNARY MIXT OF AN 2,532,243 1 1/1950 Ott ..260/2.5ANTIMONY COMPOUND, A HALOGEN- 2,590,211 3/1952 Rugar 252/8.1 xCONTAINING COMPOUND AND A 2,669,521 2/1954 Bierly ..106 15 BROWN];COL/WOUND 2,894,918 7/1959 Kilioran et a1. ..260/2.5 2,962,464 1 1/1960Feild .106/15 X In entor: ar es Riley, J an Mich. 2,986,535 5/1961Jacobson ..260/2.5 3,137,745 6/1964 Johnstone ..260/2.5 X [73] Assgnee'fil chem'cal Cmpan 3,188,295 6/1965 Ballast ..260/2.5 3,269,962 8/1966EiChOrn ....260/2.5 [22] Filed; June 27, 1968 3,331,797 7/1967 Kopetz eta1. .....260/28.5 3,194,854 7/1965 Smith ...260/2.5 X 1 pp 740,6753,558,532 1 1971 Sundquist et al. ..260/2,5

Related Application Data Primary Examiner-John T. Goolkasian [63]Continuation-impart of Ser. No. 606,579, Jan. 3, Assistant ExaminerDFltltsch 1967 abandoned Attorney-Gr1swold & Burdlck, Richard G.Waterman, Lloyd E. Hcssenaur and Sidney J. Walker [52] U.S. Cl...260/2.5 FP, 252/8.1, 260/2.5 E,

260/2.5 HA, 260/28.5 AV, 260/45.7 R, 260/45.7 [57] ABSTRACT PS, 260/45.7P, 260/45.7 S, 260/45.75 R, 260/DIG. Compositions of the class offlame-retardant or self-extin- 24 guishing ethylene and vinyl alkanoatecopolymer foams, use- [51] Int. Cl ..C08f 15/02, C09k 3/28 ful asinsulation, are described. Said foams are relatively [58] Field ofSearch... 252/8,1, 3; 106/15 FP; lightly loaded with either a binaryflame retardant mixture of 161/403; 117/137; 260/2.5 R, 2.5 FP, 28.5 R,28.5 AV, DIG. 24, 45.7 R, 45.7 PS, 45.7 P, 45.7 S, 45.75 R

( 1) an antimony compound and (2) a halogen-containing aliphatic orcycloaliphatic compound of particular specificity or a ternaryflame-retardant mixture including (1) and (2), and, (3) abromine-containing aromatic or acyclic compound of particularspecificity.

1 1 Claims, 1 Drawing Figure INVENTOR. Char/e5 F. Ra/ey, Jr

QTTORNEV SELF-EXTINGUISHING ETHYLENE COPOLYMER FOAMS COMPRISING ATERNARY MIXTURE OF AN ANTIMONY COMPOUND, A HALOGEN-CONTAINING COMPOUNDAND A BROMINE COMPOUND The present invention is a continuation-impart ofcopending application Ser. No. 606,579, filed Jan. 3, 1967 nowabandoned.

This invention relates to flame-retardant or self-extinguishing ethylenecopolymer foams.

It has been proposed heretofore to impart flame-retardancy tothermoplastic polymer compositions by incorporating various materials inthe polymer. Flame-retardance has been obtained, for instance, bycombining with the polymer a solid chlorinated hydrocarbon of highchlorine content such as chlorinated paraffin, and an inorganicflame-retardant substance such as antimony oxide in critical proportionsto each other and tothe polymer. Such compositions are described in U.S.Pat. Nos. 2,480,298; 2,590,21 l and 2,669,521.

These prior art compositions are generally directed to the solid polymerbut are not satisfactory for the making of flameretardant andself-extinguishing foamed ethylene polymers.

Accordingly, it is a primary object of this invention to provideflame-retardant or self-extinguishing foamed ethylene copolymercompositions which are not heavily loaded with flame-retardant agentsyet produce foamed products possessing highly satisfactoryself-extinguishing times of about 3 or 4 seconds or less. Another objectis to provide flame-retardant or self-extinguishing ethylene copolymercompositions which contain a smaller and more desirable concentration offlame-retardant agents than have the heretofore known flameretardantethylene polymer compositions.

l have now discovered that when to parts by weight of a mixture offlame-retardant agents containing in certain amounts (1) an antimonycompound and (2) a halogen-containing aliphatic or cycloaliphaticcompound having a hydrogen atom or halogen atom attached to a carbonatom alpha to a halogen-substituted carbon atom and containing fromabout 50 to 80 percent by weight of halogen, is intimately incorporatedin 100 parts by weight of an ethylene copolymer foam, unexpectedly goodself-extinguishing properties are obtained.

In addition, I have found that when 10 to 15 parts by weight of aternary mixture of flame-retardant agents containing in certain amountscompounds l) and (2) as well as (3) a bromine-containing aromatic oracyclic compound, said acyclic compound containing vinylic bromine ornot having a hydrogen atom or bromine atom attached to a carbon atomalpha to a bromine-substituted carbon atom, is intimately incorporatedin 100 parts by weight of the ethylene copolymer foam, unexpectedly goodself-extinguishing properties are obtained.

in accordance with the present invention, the binary flameretardantsystem incorporated in an ethylene copolymer foam contains theflame-retardant or self-extinguishing agents in a weight ratio range ofbetween 0.5 to 1.0 and 1.5 to 1.0 inclusive of (1) to (2) and theternary system contains the agents in the ratios within the area ABCDEFof the accompanying drawing.

The accompanying drawing is a trilinear diagram wherein the antimonycompound is (l), the halogen-containing aliphatic or cycloaliphaticcompound having a hydrogen atom or halogen atom attached to a carbonatom alpha to a halogen-substituted carbon atom and containing fromabout 50 to 80 percent by weight of halogen is (2), and thebrominecontaining aromatic or acyclic compound, said acyclic compoundcontaining vinylic bromine or not having a hydrogen atom or bromine atomattached to a carbon atom alpha to a bromine-substituted carbon atom is(3). The equations shown show the limiting ratios of the components (1),(2) and (3) within the area ABCDEF; for example: r&=0.5.

When the binary flame-retardant system is employed, the extreme weightlimits of components (1) and (2) are from 3.3 to 9.0 parts by weight of(1) and from 4.0 to 10.0 parts by weight of (2) per 100 parts by weightof copolymer. These parts by weight are subject to the above definedweight ratio range. When the ternary flame-retardant system is employed,the extreme weight limits are from 2.7 to 9.4 parts by weight of (l),2.5 to 9.9 parts by weight of (2), and from 0.3 to 3.6 parts by weightof (3), all per 100 parts by weight of copolymer. These parts by weightare subject to the above defined ratios within the area ABCDEF of theaccompanying drawing.

Surprising as it may seen, use of either of the binary or ternaryflame-retardant systems in admixture in the proportions hereinprescribed provide uniquely superior and entirely unpredictable results.Thus, by preparing the foamed ethylene copolymer compositions of theinvention, products of unexpectedly and significantly superiorself-extinguishing properties are obtained.

The ethylene copolymers to be employed in the invention can be anynormally solid resinous thermoplastic ethylene polymer such ascopolymers of ethylene and from about 1 to about 30, preferably fromabout 3 to about 10, weight per cent of a vinyl alkanoate such as vinylacetate, vinyl propionate, and vinyl butyrate, and copolymers ofethylene and from about 1 to about 30, preferably from about 3 to about10, weight percent of a lower alkyl (C to C acrylate or methacrylatesuch as, for example, methyl acrylate, ethyl acrylate, propyl acrylate,isopropyl acrylate, butyl acrylate, methyl methacrylate and butylmethacrylate.

The antimony compounds useful in the practice of the invention includeantimony trioxide, antimony pentoxide, antimony sulfide and the like.

The halogen-containing aliphatic or cycloaliphatic compounds having ahydrogen atom or halogen atom attached to a carbon atom alpha to ahalogen-substituted carbon atom which can be used in the practice of theinvention include the chlorine-containing self-extinguishing compoundssuch as hexachlorocyclohexane, a chlorinated paraffin wax containingbetween about 50 and percent by weight of chlorine and the like, as wellas the bromine-containing compounds such aspentabromomonochlorocyclohexane, hexabromocyclohexane,tris(2,3-dibromopropyl) 8c brominated polybutadienc latex and the like.Preferably, these compounds contain from 3 to 40 carbon atoms.

The bromine-containing compounds which can be used in the practice ofthe invention include aromatic compounds such as hexabromobenzene,pentabromomocochlorobenzene, tetrabromodichlorobenzene,tetrabromobenzene, pentabromophenol, tetrabromobisphenol-A, bis(pentabromophenyl) ether, and tribromophenol, as well as acycliccompounds having vinylic bromine or not having a hydrogen atom orbromine atom attached to a carbon atom alpha to a bromine-substitutedcarbon atom, such as pentaerythrityl tetrabromide,2,2-bis(bromomethyl)-1-bromo-3-hydroxypropane, and the like. Preferably,the aromatic compounds contain from six to 12 carbon atoms in thearomatic ring structure, and the acyclic compounds contain from three to15 carbon atoms.

In the practice of the present invention, a homogeneous mobile orflowable gel composition of a heat-plastified or molten normally solidethylene copolymer, 10 to 15 parts per parts of resin of either thebinary or ternary flame-retardant mixture hereinbefore described, and avolatile organic foaming agent is formed under pressure and thereaftersaid composition is extruded into a zone of lower pressure sufficient tocause expansion of the extruded material with resultant formation of aflame-retardant foamed ethylene copolymer article composed for the mostpart of uniformly fine individuallyclosed thin-walled cells.

Small amounts, e.g. from 0.1 to 2 percent by weight of the ethylenecopolymer, of additives such as aluminum stearate, zinc stearate,indigotin, blue copper phthalocyanine or other agents such as finelydivided calcium silicate, diatomaceous earth, calcium carbonate, bariumsulfate and the like can be employed advantageously as nucleatingagents, but are not required in the invention.

The mobile or flowable gel is prepared by placing the ingredients underpressure of the foaming agent, suitably at temperatures above thecrystalline melting point of the ethylene copolymer, e.g. at from 90 to200 C., such as by heating the ingredients in admixture with one anotherin a pressure resistant vessel or an extruder until a homogeneous orsubstantially uniform flowable gel is obtained. Thereafter, the gel isextruded into a zone of sufficiently lower pressure such as theatmosphere to cause the extruded material to expand with resultantformation of a cellular or foamed body.

The gel is preferably extruded at a temperature near or above themelting point of the ethylene copolymer, but higher or lowertemperatures can be used The temperature at which the gel is extrudedinto the zone of lower pressure will vary depending in part upon thesize and arrangement of the apparatus used, the rate of extrusion of thegel, the melting point of the ethylene copolymer and the proportion andkind of volatile organic foaming agent or other additives employed.

In general, the gel can be extruded at a temperature of from about 25 C.below the temperature at which crystallization of the ethylene copolymercauses an observable cloudiness in the gel, up to a temperature of 25 C.above the melting point of the ethylene copolymer. The temperature atwhich crystallization of the ethylene copolymer causes a cloudiness ofthe gel can be determined readily by a simple test such as by sealingweighed amounts of the ethylene copolymer and the foaming agent in aglass tube, heating the mixture to a temperature above the melting pointof the ethylene copolymer to obtain a transparent uniform gel, thencooling or allowing the gel to cool and observing the temperature atwhich the gel becomes hazy or cloudy. The temperature at which anobservable cloudiness of the gel occurs is hereinafter referred to asthe cloud point.

The pressure to be maintained on the gel prior to its extrusion in azone of lower pressure should be at least as high as that of the vaporpressure of the volatile organic foaming agent and sufficient to preventfoaming in the extruder or discharge orifice. Pressures of from about300-2,000 pounds per square inch or higher, gauge pressure, can be used.

The volatile organic foaming agent should be a non-solvent or poorsolvent for the ethylene copolymer such as 1,2-dichlorotetrafluoroethane, dichlorodifluoromethane, isobutane, methylchloride, 1,1,l-trifluoroethane, ethylidene fluoride, perfluoropropane,2,2-difluoropropane, each alone or mixtures thereof, and the like, butone that dissolves in the polymer in an amount up to about 30 percent byweight sufficient to form a mobile or flowable gel and expand theextruded gel to produce a cellular or foamed body. The foaming agent canbe employed in amounts from 0.05 to 0.5 gram mole per 100 grams of theethylene copolymer.

In practice, the flame-retardant ethylene copolymer foams can beprepared by feeding solid granules of the ethylene copolymer togetherwith the binary or ternary flame-retardant mixture in the desiredproportion, into the feed hopper of a plastic extruder wherein thepolymeric material is pressed and heated to its melting temperature andis forwarded by means of the screw into a mixing and blending zonewherein the heatsoftened material is blended under pressure with avolatile organic foaming agent such as l,2-dichlorotetra-fluoroethanealso fed to the mixing and blending zone of the extruder. The resultingmixture is blended into a homogeneous mobile gel and is brought to atemperature between about 90 and 200 C., preferably from 90l20 C., thenis extruded into a zone of lower pressure, suitably the atmosphere,wherein the extruded material expands with resultant formation of a foamof substantially uniform fine individually closed thin-walled cells.

An alternative method of foaming the composition is to incorporate adecomposable blowing agent such as azodicarbonamide, benzene sulfonylhydrazide, oxybis benzene sulfonyl hydrazide, ammonium carbonate,N,N'-dinitroso N,N- dimethyl terephthaamide, and the like, in thepolymer composition along with the flame-retardant additives, heatingthe mixture above the softening point of the polymer to thedecomposition point of the blowing agent, and permitting the liberatedgas to expand the polymer composition into a foamed state.

The flame-retardant foamed ethylene copolymers of the invention areuseful as insulation, in packaging application, for forming gaskets, assealant backers in certain types of construction, etc.

The following non-limiting examples serve to illustrate my invention.

EXAMPLE I One hundred parts by weight of a copolymer of ethylene and 4weight percent vinyl acetate having a melt index of 2, together with 7.5parts by weight of antimony trioxide and 7.5 parts by weight ofchlorinated paraffin wax containing about 70 percent chlorine wascompounded thoroughly at a temperature of 250-300 F. in a Banbury mixerthen cooled and ground up into fine particles. The compounded mixturewas fed into a plastics extruder at a rate corresponding to 5 pounds ofthe mixture per hour. The plastics extruder employed in the experimentcomprised a barrel having a 1% inch diameter screw equipped with amixing head similar in design to that described in US. Pat. No.2,453,088 and a sealing plate positioned mid-way of the screw. An inletto the barrel of the extruder was provided adjacent to the sealing platefor feed of a volatile organic compound as blowing agent into the barreland into the heat-plastified ethylene copolymer. The sealing plateformed a constricted passageway between the rim of the plate and thebore of the barrel so that flow of the heatplastified ethylene copolymerthrough the constricted passageway by pressure of the flights of thescrew formed an effective plastic seal against counter-current flow orleakage of the volatile organic compound from the extruder. Theheatplastified ethylene-vinyl acetate copolymer formulation wasforwarded under pressure of the screw around the sealing plate and intothe second section of the barrel of the extruder wherein it was mixedwith 1,2-dichlorotetrafluoroethane as a foaming agent fed thereto at arate of 0.9 pounds per hour. The resulting mixture was blended underpressure, e.g. 500-600 pounds per square inch gauge, principally byaction of the mixing head on the screw of the extruder, into a uniformgel composition and was brought to a temperature between and 1 10 C.,then forced through a discharge orifice of A X /3 inch cross-sectioninto the atmosphere. The extruded material was allowed to expand freelyin the air. The ethylenevinyl acetate copolymer foam product was acellular oval rod having a cross-section of 18 X 13 mm. and was composedof substantially uniform -fine individually-closed thin-walled cells.The foam had a density of about 2.7 pounds per cubic foot.

The product was tested for its self-extinguishing properties by thefollowing procedure: a sample of the product was inclined at a 30 anglebelow the horizontal while in a draftfree enclosure; a gas flame l-inchhigh was applied to the lower end of the sample until it was ignited;the flame was then removed. The time for the ignited foam to extinguishitself was measured; this procedure was repeated a plurality of times onthe foam. The self-extinguishing times reported are the average of 34tests.

The ethylene-vinyl acetate copolymer foam had a self-extinguishing timeof 1.1 seconds.

A polyethylene foam prepared and tested under similar conditions andcontaining 8 parts per 100 parts of polymer of antimony trioxide and 8parts of chlorinated parafiin wax containing about 70 percent by weightof chlorine had a selfextinguishing time of 10.1 seconds.

EXAMPLE II Following the same procedure as in Example I, aflame-retardant foam composition according to the invention of acopolymer of ethylene and 4 weight percent vinyl acetate was preparedexcept for using 6.5 parts per 100 parts of polymer of antimony trioxideand 6.5 parts per 100 parts of polymer of chlorinated paraffin waxcontaining about 70 percent chlorine. A self-extinguishing time of 2seconds was obtained.

EXAMPLE 111 Following the same procedure as in Example 1, aflame-retardant foam composition according to the invention of acopolymer of ethylene and 4 weight percent vinyl acetate was preparedexcept for using 5.5 parts per 100 parts of polymer of antimony trioxideand 5.5 parts per 100 parts of polymer of chlorinated paraffin waxcontaining about 70 percent chlorine. A self-extinguishing time of 3.9seconds was obtained.

EXAMPLE IV EXAMPLE V Following the same procedure as in Example I, aflame-retardant foam composition according to the invention of acopolymer of ethylene and 4 weight percent vinyl acetate was preparedexcept for using a ternary flame-retardant system containing 7.5 partsper 100 parts of polymer of antimony trioxide, 6.25 parts per 100 partsof polymer of chlorinated paraffin wax containing about 70 per centchlorine, and 1.25 parts per 100 parts of polymer of hexabromobenzene. Aselfextinguishing time of 0.5 second wasobtained.

EXAMPLE VI Following the same procedure as in Example I, aflame-retardant foam composition according to the invention of acopolymer of ethylene and 4 weight percent vinyl acetate was preparedexcept for using a ternary flame-retardant system containing 6.6 partsper 100 parts of polymer of antimony trioxide, 4.4 parts per 100 partsof polymer of chlorinated paraffin wax containing about 70 per centchlorine, and 2.2 parts per 100 parts of polymer of hexabromobenzene. Aselfextinguishing time of 1.4 seconds was obtained.

EXAMPLE VII Following the same procedure as in Example I, aflame-retardant foam composition according to the invention of acopolymer of ethylene and 4 weight percent vinyl acetate was preparedexcept for using a ternary flame-retardant system containing 6.6 partsper 100 parts Of polymer of antimony trioxide, 5.5 parts per 100 partsof polymer of chlorinated paraffin wax containing about 70 percentchlorine, and 1.1 parts per 100 parts of polymer of hexabromobenzene. Aselfextinguishing time of 0.9 second was obtained.

EXAMPLE VIII Following the same procedure as in Example I, aflame-retardant foam composition according to the invention of acopolymer of ethylene and weight percent ethyl acrylate is preparedexcept for using a binary flame-retardant mixture containing 7.8 partsof hexachlorocyclohexane per 100 parts of polymer and 3.9 parts ofantimony trioxide per 100 parts of polymer. A self-extinguishing time of3 seconds is obtained.

EXAMPLE IX Following the same procedure as in Example I, aflame-retardant foam composition according to the invention of acopolymer of ethyleneand 2.5 weight percent vinyl acetate was preparedexcept for using a binary flame-retardant system containing 4.26 partsper 100 parts of polymer of antimony trioxide and 3.97 parts per 100parts of polymer of chlorinated paraffin wax containing about 70 percentchlorine. A selfextinguishing time of 1.1 seconds was obtained.

I claim:

1. A foamed ethylene copolymer article containing a mixture ofself-extinguishing agents consisting essentially of (1) an antimonycompound selected from the group consisting of antimony trioxide,antimony pentoxide and antimony sulfide and (2) a halogen-containingaliphatic or cycloaliphatic compound having a hydrogen atom or halogenatom attached to a carbon atom a to a halogen substituted carbon atomand containing from 50 to weight percent of halogen, characterized inthat the copolymer composition is a copolymer of ethylene and from 1 to30 weight percent of a vinyl alkanoate or a lower alkyl acrylate ormethacrylate, a third component (3) a bromine-containing aromatic oracylic compound which has vinylic bromine or does not have a hydrogen orhalogen atom attached to a carbon atom a to a bromine-substituted carbonatom, in which case the components of the ternary mixture ofself-extinguishing agents are present in the proportions which liewithin the area ABCDEF of the accompanying drawing, the mixture ofselfextinguishing agents being present in an amount of from 10 to 15parts by weight per parts of the copolymer and components (1) and (2)having a weight ratio range of between 0.5 to 1.0 and 1.5 to 1.0,inclusive, of(1) to (2).

2. The article of claim 1, wherein the polymer contains from 3 to 30weight percent of vinyl acetate or ethyl acrylate.

3. The article of claim 1, wherein the halogen of compound (2) ischlorine or bromine.

4. The article of claim 3, wherein the compound of (2) con tains from 3to 40 carbon atoms.

5. The article of claim 1, wherein the aromatic compound of (3) containsfrom six to 12 carbon atoms in the aromatic ring structure, and theacyclic compound of (3) contains from three to 15 carbon atoms.

6. The article of claim 1, wherein the compound of (2) contains fromthree to 40 carbon atoms and the halogen is chlorine or bromine, thearomatic compound of (3) contains from six to 12 carbon atoms in thearomatic ring structure, and the acyclic compound of (3) contains fromthree to 15 carbon atoms.

7. The article of claim 1, wherein the antimony compound is antimonytrioxide.

8. The article of claim 1, wherein the compound of (2) is chlorinatedparaffin wax containing about 70 percent chlorine.

9. The article of claim 1, wherein the compound of (3) ishexabromobenzene.

10. The article of claim 1 which contains 7.5 parts by weight ofantimony oxide, 6.25 parts by weight of chlorinated paraffin waxcontaining about 70 percent chlorine, and 1.25 parts by weight ofhexabromobenzene.

11. A foamed ethylene copolymer article containing a mixture ofself-extinguishing agents consisting essentially of (1) an antimonyoxide selected from the group consisting of antimony trioxide, antimonypentoxide and antimony sulfide, and (2) a member selected from the groupconsisting of: a chlorinated parafiin wax containing between about 50and 80 percent by weight chlorine, hexachlorocyclohexane,pentabromomonochlorocyclohexane, hexabromocyclohexane, tris(2,3-dibromopropyl)phosphate and brominated polybutadiene latex,characterized in that the copolymer composition is a copolymer of fromabout 99 to 70 weight percent ethylene and from 1 to 30 weight percentof a vinyl alkanoate or a lower alkyl acrylate or methacrylate, andcomponents (1) and (2) being present in a weight ratio between 0.5 to 1and 1.5 to l, inclusive, of (1) and (2), a third component (3) a brominecompound selected from the group consisting of hexabromobenzene,pentabromomonochlorobenzene,

tetrabromodichlorobenzene, tetrabromobenzene, pentabromophenol,tetrabromobisphenolbA, bis(pentabromophenyl)ether and tribromophenoi,acyclic compounds having vinylic bromine or not having a hydrogen atomor bromine atom attached to a carbon atom a to a brominesubstitutedcarbon atom, such as pentaerythrityl tetrabromide,2,2-bis(bromomethyl)1-bromo-3-hydroxy-propane being present in an amountof from about 10 to 15 parts by weight per parts by weight of thecopolymer.

2. The article of claim 1, whereIn the polymer contains from 3 to 30weight percent of vinyl acetate or ethyl acrylate.
 3. The article ofclaim 1, wherein the halogen of compound (2) is chlorine or bromine. 4.The article of claim 3, wherein the compound of (2) contains from 3 to40 carbon atoms.
 5. The article of claim 1, wherein the aromaticcompound of (3) contains from six to 12 carbon atoms in the aromaticring structure, and the acyclic compound of (3) contains from three to15 carbon atoms.
 6. The article of claim 1, wherein the compound of (2)contains from three to 40 carbon atoms and the halogen is chlorine orbromine, the aromatic compound of (3) contains from six to 12 carbonatoms in the aromatic ring structure, and the acyclic compound of (3)contains from three to 15 carbon atoms.
 7. The article of claim 1,wherein the antimony compound is antimony trioxide.
 8. The article ofclaim 1, wherein the compound of (2) is chlorinated paraffin waxcontaining about 70 percent chlorine.
 9. The article of claim 1, whereinthe compound of (3) is hexabromobenzene.
 10. The article of claim 1which contains 7.5 parts by weight of antimony oxide, 6.25 parts byweight of chlorinated paraffin wax containing about 70 percent chlorine,and 1.25 parts by weight of hexabromobenzene.
 11. A foamed ethylenecopolymer article containing a mixture of self-extinguishing agentsconsisting essentially of (1) an antimony oxide selected from the groupconsisting of antimony trioxide, antimony pentoxide and antimonysulfide, and (2) a member selected from the group consisting of: achlorinated paraffin wax containing between about 50 and 80 percent byweight chlorine, hexachlorocyclohexane, pentabromomonochlorocyclohexane,hexabromocyclohexane, tris(2,3-dibromopropyl)phosphate and brominatedpolybutadiene latex, characterized in that the copolymer composition isa copolymer of from about 99 to 70 weight percent ethylene and from 1 to30 weight percent of a vinyl alkanoate or a lower alkyl acrylate ormethacrylate, and components (1) and (2) being present in a weight ratiobetween 0.5 to 1 and 1.5 to 1, inclusive, of (1) and (2), a thirdcomponent (3) a bromine compound selected from the group consisting ofhexabromobenzene, pentabromomonochlorobenzene,tetrabromodichlorobenzene, tetrabromobenzene, pentabromophenol,tetrabromobisphenol-A, bis(pentabromophenyl)ether and tribromophenol,acyclic compounds having vinylic bromine or not having a hydrogen atomor bromine atom attached to a carbon atom Alpha to a bromine-substitutedcarbon atom, such as pentaerythrityl tetrabromide,2,2-bis(bromomethyl)-1-bromo-3-hydroxy-propane and the like, and (1),(2) and (3) are present in proportions which lie within the area ABCDEFof the accompanying drawing, the mixture of self-extinguishing agents(1), (2) and (3) being present in an amount of from about 10 to 15 partsby weight per 100 parts by weight of the copolymer.